One of the important aspects of present-day data processing systems is their capability of monitoring the operation of all units within the system and taking corrective action in the event of a fault or failure. Diagnostic testing and error-handling functions are typically assigned to a maintenance processor to which transmissions indicative of errors are directed in the event of a system or subsystem anomaly. Such error recovery schemes may include the monitoring of parity, time-out, bus and internal memory errors, error correcting codes, etc. For descriptions of examples of the use of such maintenance processors and the compilation of error data by units connected to a system bus attention may be directed to the U.S. Patents to Wilber et al., U.S. Pat. No. 3,921,141, Hopkins et al., U.S. Pat. No. 3,015,246, Kaminski et al., U.S. Pat. No. 4,176,394, Huettner et al., U.S. Pat. No. 3,810,120, and Getson et al., U.S. Pat. No. 4,159,534. Unfortunately, conventional approaches to error reporting usually involve the assembly of a separate error message containing prescribed address and data segments for transmission to the maintenance processor. As such, system complexity is increased and error reporting speed suffers due to the need for an intermediate message handling scheme.